Research clearly indicates that attention-deficit hyperactivity disorder (ADHD) is a common behavioral concomitant of Tourette's syndrome (TS) and chronic tic disorder in child patients. Unfortunately, the most safe, effective, and widely used pharmacological treatment for ADHD, namely methylphenidate, has generally been thought to exacerbate tics and therefore to be contraindicated in such patients. Because (a) the pharmacological alternatives to methylphenidate are often associated with increased risk of adverse drug reactions or are less efficacious for ADHD behaviors, and (b) there is very little controlled research on the long-term use of stimulants in children with tic disorder, there is a compelling need to examine the safety and efficacy of methylphenidate for ADHD in children with tic disorder (ADHD/+tics) and to develop drug evaluation procedures for clinical application. The primary objectives of the proposed study are to (1) assess short- and long-term effects of stimulant drug therapy for children with ADHD/tics+, and (2) describe developmental changes in tics, ADHD and antisocial behaviors, and mood and anxiety symptoms. The proposed study is a continuation of a long-term follow-up study of 82 children between 6 and 12 years of age who have ADHD/+tics and who will (or have) participate (d) in an 8-week, placebo-controlled, double-blind methylphenidate evaluation. Drug response for both ADHD and tic disorder symptoms is assessed using direct observation procedures in a simulated clinic classroom and with physician, teacher, and parent rating scales. Systematic assessment of symptom status is conducted at 6-month intervals for a minimum of 2 years and then at 12-month intervals for an additional 3 years (i.e., minimum of 5 years). To evaluate the impact of tic severity and comorbid internalizing and externalizing symptoms on clinical outcome, children with ADHD/+tics will be compared with an additional sample of children with ADHD/-tics at ages 11 and 16 years.